Power cycling tests for accelerated ageing of ultracapacitors

In this paper, a test methodology is presented and evaluated in order to quantify the lifetime of ultracapacitors in case of active power cycling. The test profiles are specified for taking into account both the high charge-discharge levels and the periodicity of typical HEV applications. Before cycling, preliminary tests have been done with Maxwell BCap 2600F devices and have proved that pulsed current profiles can be predetermined in order to induce a given self-heating. Then, during power cycling, periodic characterization tests have been done in order to follow the evolution of cell parameters. The results at 25,000 cycles illustrate that impedance real part and capacitance are significant parameters for ageing quantification. Furthermore, the trend of these results shows that the self-heating acts as an accelerating factor for ageing.